Spinner construction for an aeronautical propeller



July 24, 1956 c. B. SMITH 2,755,868

SPINNER CONSTRUCTION FOR AN AERONAUTICAL. PROPELLER Filed Sept. 17, 1953 2 Sheets-Sheet 1 FIG.

C. B. SMITH July 24, 1956 SPINNER CONSTRUCTION FOR AN AERONAUTICAL PROPELLER Filed Sept. 17, 1953 INVENTOR. Cl/AELFS 5. SMITH BY 1 37% Ll ll ATTOIP/YE'Y nited States Patent SPINNER CONSTRUCTION FoR AN AERONAUTICAL PROPELLER' Charles B. Smith, Windsor, Cnn., assignor to United Aircraft Corporation, East Hartford, Conn, a corporation of Delaware Application September 17, 1953, Serial No. 380,727

4 Claims. (Cl. 170159) This invention relates to devices adapted to improve the propeller performance of high speed aircraft and, more specifically, to a propeller spinner construction which is particularly adapted for the aforesaid purpose.

The study of problems relating to the design of aeronautical propeller blades for high subsonic, sonic and supersonic flight speeds has established that blades of thin section are highly desirable from the standpoint of aerodynamic e'lhciency. However, in the design of propeller blades structural and strength problems must be considered and solved as well as the problems relating to aerodynamic efiiciency. In the design of blades for high speed flight, it has been found difiicult to provide a thin section blade which meets all of the structural requirements and the structurally sound blades developed have lacked efficiency in high speed operation because of increased thickness. More specifically, a blade having desirably thin sections throughout the major portion of its length must be provided with a relatively thick shank in order to satisfy the strength requirements. While relatively thick-shank blades are aerodynamically satisfactory on aircraft which do not approach sonic speeds, such blades suffer a loss of efliciency at speeds approaching sonic levels because of the excessive drag on the shank encountered at such high speeds.

In accordance with the present invention there is provided a propeller spinner construction which features fin means adapted to cooperate with the shank portions of the propeller blades to provide airfoil-forming extensions therefor, whereby the chordwise length-to-thickness ratio of the said shank portions is effectively increased so as to reduce drag at the higher flight speeds.

Accordingly, it may be said that it is the general object of the invention to provide a propeller spinner construcion which will improve the aerodynamic performance of the propeller at high flight speeds.

Another object of the invention is to provide a propeller spinner construction which makes possible the use of relatively thick-shank propeller blades on high speed aircraft.

A more specific object of the invention is to increase the aerodynamic efiiciency of the shank portion of the blades of a propeller by the provision of a spinner having airfoil-forming fins capable of producing a thrust component which will result in a net increase in the propulsive efficiency of the propeller assembly.

Other objects and advantages of the invention will become apparent to those skilled in the art from the followin description with reference to the accompanying drawings which, by way of preferred examples only, illustrate one specific embodiment of the invention and in which,

Fig. l is a perspective view of a spinner incorporating the features of the present invention;

Fig. 2 is an enlarged fragmentary top planview of the spinner;

Fig; 3 is a fragmentary longitudinal cross sectional view of the spinner, taken generally as indicated by line 2,755,868 Patented July 24, 1956 33 of Fig. 2, but showing a complete vertical section along the curved major dimension of one of the fins;-

Fig. 4 is a fragmentary transverse cross sectional view of the spinner, taken as indicated by the line 44 of Fig. 2;

Fig. 5 is an enlarged fragmentary cross sectional detail view, taken through one of the fins, as indicated by line 55 of Fig. 4-; and

Fig. 6 is another fragmentary transverse sectional view of the spinner, taken as indicated by line 66 of Fig. 2.

The invention may be described without specific reference to the drawings as comprising a conical propeller spinner having a plurality of fins corresponding in mm her to the blades of the propeller assembly upon which the spinner is mounted. Each of the said fins constitutes an airfoil member associated with one of the blades of the propeller. Each fin tapers outwardly from the tip or nose of the spinner toward its respective blade to provide an airfoil of increasing surface area from the tip of the spinner to the propeller blade. From an aerodynamic standpoint each said fin can be compared to the so-called"Delta wing.

The fin is formed as a sheet metal shell, generally triangular in plan form, with the trailing edges spaced apart and closed by a generally triangular bulkhead which is provided with a transverse arc so as to surround the leading edge portion of the shank of the blade. Accordingly, each fin provides a forwardly projecting airfoil-forming extension for the shank of the respective propeller blade. It should be noted that each fin is curved or twisted along its major dimension, i. e., from the tip of the spinner to the blade, to provide a self-formed angle of attack or pitch angle for the fin which varies over the length of the fin and is thus slightly different in adjacent transverse sections through the fin. The twist or pitch of the fin, and particularly the pitch angle adjacent the trailing edge of the fin, is preformed to conform generally to the angle of twist of the shank of the blade and each fin is arranged upon the spinner to form a substantially continuous, streamline airfoil extension of the blade shank when the blade is set about its pitch change axis for optimum high speed performance.

With more specific reference to Fig. 1, there is'shown a conical spinner 10 which is mounted upon a propeller hub to extend forwardly from the engine cowling 12. A plurality of fins 14, 14 (4 shown) are provided on the spinner to taper outwardly from the tip thereof toward the rear thereof. Each of said fins is in the form of a generally triangular sheet metal shell comprising a sheet 16 which is folded upon itself to define a tapered leading edge is with the inner edges 21), 20 of the sheet secured to the spinner as will be described and with the trailing edges 22,22 spaced apart across the forward edge of a substantially circular opening 24 in the spinner through which the shank portion of a propeller blade extends. A panel or bulkhead 23 is secured across the trailing edges 22, 22 and is provided with a transverse arc to surround the leading edge of said shank portion of the blade. Accordingly, there will be one such fin 14 provided for each blade of the propeller and the fins will beequally circumferentially spaced around the spinner 10.

As previously mentioned, each fin is twisted to provide a varying angle of pitch along the length of the fin. In keeping therewith, the leading edge 18 of each fin is curved in what may be termed a slight helix fromthe'tip of the spinner towards the rear thereof and with the said leading edge extending over the geometrical centerline of the fin in the direction of rotation of the propeller. The inner edges 20, 20 of the fin-forming shell 16 extend at an angle from each other with the apex of the angleat the'tip" of the spinner shell. Accordingly, the trailing edges 22, 22 of the fin intersect at a substantial angle at the leading edge and said leading edge may be flattened as shown at 26 adjacent the intersection of the said trailing edges to be in a plane substantially parallel to the longitudinal axis of the spinner.

It will be readily understood that the pitch of the fins 14, 14 provides the spinner with the aerodynamic characteristics of an air screw having a component of thrust which increases the propulsive efficiency of the propeller assembly. It will also be understood by those skilled in the art that the generally triangular swept-back form of the fins is a particularly advantageous form for wings and other airfoils in aircraft which approach and surpass the speed of sound. More specifically, the swept back or tapered leading edges of the fins reduce the component of velocity which is perpendicular to the leading edges or that component of velocity which is effective of producing the shock wave which deleteriously affects the aerodynamic characteristics of the airfoil fins. In other words, the swept back leading edges of the fins raises the speed at which the propeller assembly encounters the shock phenomena.

Turning now to specific consideration of the construction of the body or shell of the spinner 10 and with specific reference to Figs. 2 and 3, it will be noted that the said spinner may be conveniently formed from a plurality of interconnected sheet metal sections. The foremost or tip section 28 is conical and the other sections 30, 30 are frusto-conical being engaged in edge-to-edge relationship. The means interconnecting the conical section 28 and the foremost frusto-conical section 30 comprises an internally disposed ring 32 having a rim which extends across the trailing edge of the section 28 and the forward edge of the section 30, securing the same in edge-to-edge rela tionship as by rivets 34, 34. There are five such frustoconical sections shown in the illustrative example and the second and third (numbering from the front) are secured in edge-to-edge relationship by a riveted ring 32 similar .to the previously described ring 32.

The rearmost section 30 may be supported independently on the rim of an annular plate 36 which is secured to the hub 38 of the propeller rearwardly of the blades. The trailing edge of the rearmost section 30 can extend rearwardly as far as desired and the leading edge can engage or be closely spaced from the trailing edge of the adjacent section 30. The adjacent edges of the two rearmost sections 30, 30 are provided with arcuate, circumferentially spaced cut-outs which register with each other to define the openings 24, 24 through which the propeller blades 40, 40 extend.

The third and fourth sections 30, 30 are interconnected along their adjacent edges to the rim of another annular plate 42 which is secured to the propeller hub 38 forwardly of the blades. The first and second sections 30, 30 are similarly interconnected on a third annular plate 44 which has a central opening embracing the forwardly extending portion of the propeller hub 38.

It should be understood that the spinner body can be fabricated and supported in various other ways, but in any event sturdy transverse support members generally similar to the members 36, 42 and 44 should be provided for assurance that the spinner shell is rigidly supported on the propeller hub.

The fins 14, 14 should also be rigidly supported upon the shell of the spinner to Withstand the aerodynamic loads imposed thereon in flight. To effectuate rigid sup- .port of each fin, the inner edges 20, of the shellforming sheet 16 are flanged outwardly and secured to the spinner body as by rivets 46, 46 and there is also provided a plurality of spaced apart transverse bulkheads 48, 48 which are riveted to the sides of the shell as best shown in Fig. 5. Each said bulkhead 48 provides rigid transverse support to the fin and said bulkheads are spaced along each fin as shown in Fig. 3 to distribute the load in the best manner.

It should also be noted in Fig. 3 that all but the foremost bulkhead member is located adjacent a spinner sup port ring 32 or a spinner support plate 42 or 44 so that a spider 50 having radially extending arms 52, 52 (Figs. 4 and 6) can be fixed to the adjacent spinner body ring or plate as by rivets 54, 54. The arms 52, 52 extend through apertures in the spinner shell into the fins 14, 14 and are secured to the adjacent bulkhead 48. Accordingly, the bulkheads and thus the fins are mutually supported with respect to each other on the spiders 50, 50 which are fixed to the spinner body support structure.

As will be apparent by comparison of Figs. 4 and 6, adjacent spiders 50, 50 are in rotated positions with respect to each other about the axis of the spinner. This, of course, is necessitated to rigidly support the fins at the preformed pitch angle.

As previously mentioned, the twist or pitch of the fins is in keeping with the twist in the shank portions of the propeller blades and in keeping with the pitch angle to which the blades will be set for high speed flight operation. In this consideration, it is important to note that the aforedescribed spinner and fins do not in any way interfere with changes in pitch of the blades. The spinner and forwardly extending fins will not deleteriously aifect blade operation when the pitch angle of the blades is changed from the angle selected for high speed flight.

It is also important to note that the spinner-fin construction can be used with various types of propeller blades to great advantage. When any blade is set at a pitch angle wherein the shank portion of the blade is in substantial alignment with its respective fin, the said fin constitutes a streamlined airfoil extension of the blade shank as may be seen with reference to Fig. 2. The alignment of the fin and blade increases the effective chordwise length of the blade, in sections through the shank thereof, and thus increases its thinness ratio (chord length divided by thickness). It is well known that an airfoil, such as a propeller blade, with the greatest possible thinness ratio, in keeping with other considerations, offers the maximum liftwith the minimum drag. In consideration of the advantageous effect of the spinner fin on the shank section of the blade, it may be said that by increasing the effective thinness ratio of the shank, the deleterious effect of drag is encountered at higher than ordinary speeds and, thus, aerodynamic efiiciency is increased.

While as pointed out above the spinner may be used with various types of propeller blades, the blade 40, as best shown in Fig. 3, is particularly adapted to the exemplary spinner structure described. The said blade 40 is cut out at 41 so that the leading edge of the blade will overhang the fiat top portion 26 on the leading edge of the fin and thus the leading edge of the fin 14 and the leading edge of the blade form a substantially continuous line. Therefore, each fin 14 may be referred to as a swept back, forwardly extending fairing for its respective blade.

The inner end of the blade 40 is cut off as indicated by reference numeral 43 to closely overhang the spinner shell and thus maximum chordwise blade length is obtained closely adjacent the spinner shell and only the cylindrical shank of the blade is extended into the shell.

There are apparently many variations in construction which will fall within the scope of the invention. For example, in providing a fin construction for a blade which is not offset along its leading edge, it may be desirable to eliminate the flat top portion 26 on the fin and to extend the tapering leading edge 18 of the fin to the point of intersection of the trailing edges 22, 22 so that said point will lie in substantially the same radial plane as the leading edge of the blade.

Accordingly, it is not my intention to limit my invention to the specific embodiment shown and described otherwise than indicated by the claims which follow.

I claim as my invention:

1. In combination with a variable pitch aeronautical propeller assembly including a hub and a plurality of radially extending blades each of which is twisted to define a varying angle of attack at different sections therethrough, a substantially conical spinner mounted on said hub and projecting forwardly therefrom, and a plurality of radially extending fins corresponding in number to said blades and fixed on said spinner with their trailing edges corresponding in circumferential location with said blades, each of said fins being formed as a generally triangular airfoil of rearwardly increasing cross sectional area having a swept back leading edge extending from the nose of said spinner to the leading edge of its respective blade and having spaced apart trailing edges disposed on opposite sides of the shank portion of its respective blade with said trailing edges extending outwardly and forwardly toward the leading edge of the fin, each of said fins also being twisted to define a varying angle of attack along its leading edge with its said angle of attack at its trailing edges conforming generally to the angle of attack of the shank portion of its respective blade when the blade is set at a pitch angle in keeping with high speed flight operation, whereby each of said fins overlies the leading edge of the shank portion of its respective blade and constitutes a forwardly projecting airfoil-forming extension thereof by increasing the effective chordwise length-to-thickness ratio of the said shank portion.

2. The combination in an aeronautical propeller assembly comprising a hub and a plurality of radially extending blades, each of which blades is cut out to provide an offset leading edge whereby its chordwise length is reduced adjacent its shank, a substantially conical spinner mounted on said hub and projecting forwardly therefrom, and a plurality of radially extending fins corresponding in number to said blades and fixed to said spinner with their trailing edges corresponding in circumferential location with said blades, each of said fins being formed as an airfoil of rearwardly increasing cross sectional area and having a swept back leading edge extending from the nose of the spinner to the oifset on the leading edge of its respective blade, each fin also having a portion extending between its leading and trailing edges which portion fits within the ofiset of its respective blade and each fin also having spaced apart trailing edges disposed on opposite sides of the shank portion of its respective blade, whereby each fin constitutes a forwardly projecting airfoil-forming extension of the shank portion of its respective blade by increasing the effective chordwise length-to-thickness ratio of the said shank portion.

3. In an aeronautical propeller assembly including a hub and a plurality of radially extending blades, the combination comprising a substantially conical spinner shell projecting forwardly from said hub, a plurality of spaced apart transverse plates secured within said shell and secured to said hub, a plurality of radially extending fins corresponding in number and general circumferential location with said blades, each of said fins comprising a sheet metal sheet formed as a swept back airfoil having a generally triangular cross section of rearwardly increasing cross sectional area with the inner edges of each fin shell secured to the spinner shell and with the trailing edges of each fin shell disposed on opposite sides of the shank portion of its respective blade, a plurality of bulkheads secured within each fin shell in spaced apart relationship, there being one bulkhead disposed adjacent each of said spinner support plates, and a spiderlike support member secured to each of said plates having a plurality of arms corresponding in number to said fins and extending through said spinner shell and secured to the adjacent bulkheads of said fins, each of said bulkheads in each fin being rotated with respect to adjacent bulkheads and adjacent spider-like support mem bers being equally rotated with respect to each other whereby each of said fins is supported in a twisted position of varying angle of attack.

4. In an aeronautical propeller assembly including a hub and a plurality of radially extending blades having leading edges which are offset rearwardly adjacent the blade shanks, the combination comprising a substantially conical spinner shell projecting forwardly from the hub on the propeller axis, a plurality of axially spaced apart transverse plates secured to the hub and to the spinner shell for supporting the shell, a plurality of radially extending fins corresponding in number to the propeller blades and each comprising a sheet metal body formed as a swept back airfoil which is twisted to provide a varying angle of attack along its leading edge, and each fin being of rearwardly increasing cross sectional area with its leading edge extending from the nose of the spinner shell to the offset on the leading edge of a propeller blade and with its trailing edges disposed on opposite sides of the shank of the said blade, the angle of attack of the fin at the said ofiset being substantially the same as the angle of attack of the blade at said offset when the blade is set at a pitch angle in keeping with high speed flight operation, whereby the fin increases the effective chordwise length-to-thickness ratio of the shank of the blade, each of said fins being secured to the spinner shell and each of the said fins having a plurality of bulkheads in spaced apart locations, there being one such bulkhead located adjacent each spinner plate, and a spider-like support member secured'to each plate and having a plurality of radially extending arms, there being one such arm extending into each fin and secured to the adjacent bulkhead therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,779,186 Pavlecka Oct. 21, 1930 FOREIGN PATENTS 518,873 Great Britain Mar. 11, 1940 

